Melligaster ants are small but fierce, readily defending their nests from humans, small mammals, reptiles and especially other ants. This species tends to be less aggressive than tropical ant species, but living in the desert forces them to be rugged. Melligaster ants take a variety of food sources, including small animals, fruit, and nectar, the latter of which they convert to ant honey by feeding it to special workers. A worker becomes a replete when her nest mates begin to feed her a tremendous amount of nectar. Her gaster begins to swell and she is ferried into deep chamber up to two meters below the surface, where workers continue to feed her until she is so heavy she can no longer move. The repletes sit together on the floor or ceiling of a narrow, climate-controlled chamber and are cared for by the other members of the colony, much like the queen. Whenever a member of the colony is hungry, she will venture down into the replete chambers and nudge one of them with her antenae. This prompts the replete to regurgitate a bit of the sweet honey to feed the worker. At the end of the dry season, most of the repletes have their honey transferred to younger workers and resume their work foraging or tending to the nest. Workers and repletes only live for a few years, but the queen, and by extension the colony, can last for decades.

Melligaster ants are an unusual species which prefers small colonies of a few hundred to a few thousand individuals. They can be found in many hot, dry places in the world, including Foenara, Calidis, and especially the Etain Desert. Workers in melligaster colonies are generally brown and unassuming, and only reach a maximum size of about a centimeter or so. However, up to half of the colony's workers may serve as living storage for a honey-like substance the colony makes from gathered nectar. These storage workers, called repletes, often become so stuffed with the ant honey that the membrane between the sclerites of their abdomens become swollen and round, making them look like small striped grapes. Too heavy to move, the repletes are housed deep within the nest where the climate is stable and they are unlikely to be disturbed by predators. During droughts or food shortages, the repletes will regurgitate portions of the ant honey to feed their fellow workers. Melligaster ants are considered a delicacy in many places, including Voltar and Synara City, where they can be sold live to connoisseurs of unusual foods. They are said to have a light sweet taste and instill a sense of confidence to those who eat them, though eating one's companions is frowned upon at the Keep.